Why spider’s silk is becoming man’s best friend

LONDON – Up on the roof of professor Fritz Vollrath’s lab in the zoology department at Oxford University, there is a makeshift greenhouse in which he nurtures his favorite golden orb web spiders. Walking into the greenhouse is a little like finding yourself inside one of those Damien Hirst vitrines that dramatize fast-forward life and death.

The air is frenzied with the buzz of flies and thick with the smell of rotting fruit; look up and dozens of the mature African spiders, three inches across, are sitting pretty on elaborate webs among the foliage, clearly living the arachnid life of Riley. Vollrath points out their offspring, thousands of tiny spiderlings, scurrying about on leaves beneath.

It seems a good place to ask him exactly how he first got interested in spiders and their webs. He laughs and turns the question around. “The strange thing to me,” he says, “was always the question of why scientists were not more interested in them. I mean, here is a creature which, according to its size, can build from its own body a structure on the scale of a football pitch overnight, every night, and can catch the equivalent of an aeroplane in it. Why would you not want to study how it did that?”

There were more practical reasons, too. Vollrath was a graduate student of neurophysiology when he started looking at webs and spider silks in earnest.

“To do any small thing in neurophysiology, you had to read an awful lot of scientific literature. With spiders, I realized there was hardly any literature at all. You could just do a lot of looking.”

His fascination with spider silk began when he was at university in Munich in 1972 and the lightweight, high-tensile Olympic park, designed by Frei Otto to mimic spider-web construction, created a new imaginative framework for architecture. Vollrath, who speculated that spider silk might generate a similar revolutionary shift in the emergent field of biomaterials, was snared.

In the years since, he has probably spent more time studying how spiders spin their everyday miracles than any man alive. He has fed spiders drugs, tiny droplets of amphetamines and caffeine, and measured the dramatic disruptive effect it has on their web building. He has tested ways of training spiders with a tuning fork and discovered how to make them “write” in their webs — the Vollrath Christmas card of 1988 featured a picture of a web in which he had “taught” a spider to write the number “88” by manipulating the orientation of the web as the spider worked. Mostly, though, Vollrath has defined a pioneering area of study into the properties of spider silks that not only promises to revolutionize various polymer industries, but also could have huge potential medical benefits for humans in everything from knee replacements to nerve repair to heart transplants.

“No one was much interested in spiders when I started,” he says. “Now an awful lot of people are.” Vollrath’s silk group at Oxford has been going for about 15 years.

Quite early on, it perfected a technique to reel silk directly from the spider. He shows me a video clip of how this process works. In the film, an orb spider is tethered and encouraged to produce silk that is wound on a reel by a small mechanism. The spider can sometimes keep this up for eight hours.

Vollrath’s group can reel at different temperatures and under carefully controlled conditions. In this way, they can look at the molecular properties and X-ray diffraction patterns of the silk as it is produced. “What you find is that there is a huge correlation between the reeling conditions and the material properties,” Vollrath says, “and that gets very interesting because that is what polymer people know about.”

Spider silks are just about the toughest material on the planet. Stronger by mass than steel and more durable and flexible than Kevlar, they are also alive to ambient conditions and made to adapt and retain their tensility as humidity and temperature change. This is one of the reasons they have always made the best crosshairs in optical instruments and why webs are preserved intact in the tombs of the pharaohs. As it works, the spider adjusts the concentration of the structural components, by running fast or slow for example, so it can produce, by turns, almost crystalline, very stable silk or quite diffuse, very flexible silk, for different parts of the web.

It was when Vollrath started examining the nanostructure of the material, however, that things got really interesting.

“What we found by studying the silk as it is made,” he says, “was that at a molecular level it has something in it, a little peptide, a recurrent little motif like a melody in a tune. It is this which helps to give the silk its entirely orderly structure. We don’t know why that motif is in them, but what we do know is that same motif is also in the filaments that hold our own cells together.

“Three amino acids which give them what you might call a particular signature tune. And when the cells of our body come into contact with this pattern in the spider silks, it appears that they can recognize it. They understand it and they will react by attaching to it and growing along it.”

This little harmonic discovery has possible profound implications. As a spin-off from its lab work, Vollrath’s team partners a more commercial operation, Oxford Biomaterials, which looks at different ways to employ the silk-based technologies (using patented molecular platforms that incorporate or mimic spider and silkworm formulas). Most of these applications are medical.

“Silk from silkworms is probably the most ancient suture material,” Vollrath says. “It is thin and strong and biodegradable in the body. In all cultures, there is evidence of people using spider webs to heal wounds. Farmers out in the fields across the world have known when they get a cut to grab some spider webs and slap them on. The fibers help blood coagulate and a lot of webs have microbiocidal properties that kill bacteria. This is all homespun wisdom.

Can we make better use of this?”

To this end, Oxford Biomaterials has a range of projects under Vollrath’s co-direction. “We have, for example, a project looking at using silk to make heart muscle,” he says. “We discovered if you use a type of silk in this way and put heart cells on it, they feel at home and grow and start beating. The silk is soft. So we made a little heart muscle that can beat. And the silk is biodegradable, so you could implant something that you want to disappear once the cells have grown on it.

“The whole field of regenerative medicine could be huge. Say you have a problem with your knee. The solution now is to put a new titanium knee joint in place. That’s it. The cells will not repair anything. But to help the body repair itself, you need to put something in that will give the cells the right environment to grow. That is where silks come in. We can dissolve and reconstitute them, tune them to have mechanical properties that will match the original tissue that is there, whether it be bone or cartilage or whatever. And in that environment the human tissue will be encouraged to repair itself.”

Under the Oxford Biomaterials wing, Vollrath’s team has another project that makes meniscal implants by which they dissolve the silk in lithium bromide (“a really nasty chemical, the only thing that will touch it”) and then firm it up. The result is incredibly strong and integrates much better potentially with the human body than any plastic. These meniscal products are currently in animal trials, Vollrath says, and, given favorable outcomes, could be in humans in a year or two. In the same way, they are working on hernia meshes and bone-like structures and investigating ways in which silks can be used as a targeted carrier for drugs in the body, “tuned to slow release over weeks or months or years.”

The holy grail of this effort, also pursued by other groups around the world, is in using silks for nerve repair. “You can make very long fibers and potentially nerve cells will grow along these filaments,” Vollrath says. “We can already bridge small gaps, but not long ones. The ultimate aim is to repair spinal cord in this way.”

That goal is some way off, though Vollrath is confident it is feasible. And there are still large challenges working with spider silk. One is the impossibility of farming it on any significant scale. Unlike silkworms, whose cocoons can be nurtured and collected intensively, spiders are territorial and cannibalistic so “cannot be kept like cows in a field.”

Spider silk for this reason has never had the commercial potential of the mulberry silkworm product, though when spun it has glorious luster and color as last summer’s display of the golden spider silk cape at the Victoria & Albert museum in London showed (to make that garment, its creators Simon Peers and Nicholas Godley collected silk from more than a million orb spiders in Madagascar over a period of eight years).

One solution to this problem, Vollrath suggests, may lie in the silk of a particular Indian worm, the silk of which is near-identical in many respects to spider silk and which carries the crucial tripartite signature of amino acids also found in human cells. “These wild silks are particularly difficult to unravel,” Vollrath says — a single cocoon strand will stretch for more than a kilometer. “But I think we have found a way of doing so.”

The effort is almost always worth it, not least because of the energy saved in the silk-making process. “Most comparable polymers require a great deal of heat before they will flow,” Vollrath says. “Silk flows at ambient temperature and with very little force. We have proved that it is about a thousand times more energy efficient to produce a silk fiber than a plastic one.”

The more you talk to Vollrath, the more you have the sense of what many cultures over the years have believed — that silks of spiders and silkworms are fundamental, life-bearing materials. Is that how he sees it?

“Exactly that,” he says. “It is the building block of life in the sense that it is protein folding in action. What happens when a spider makes its web is, in effect, that a live molecule, very unstable, becomes stabilized in death. It is a denaturation process effectively. When it is alive, the molecule swims about, but once a little bit of stress is applied, a tiny chemical change made, it becomes stable and we can begin to observe that flip happen.”

In this respect, a spider’s silk behaves in a very similar way to the formation of amyloid structures in the brain — a possible cause of many neurodegenerative diseases from Parkinson’s to Alzheimer’s, an idea that brings Vollrath full circle to his original academic discipline.

“If we can work out how spiders and silkworms control how this process happens,” he says, “then we may be well on the way to understanding why it happens in humans and potential ways of stopping it.”

I’m struck talking to him how often he uses musical terminology in describing some of this science and reminded of the recent development by a Japanese researcher of concert pitch violin strings made of spider silk. It turns out that one of his researchers is also studying the tonal qualities of the material, the good vibrations “which the spider can understand down in the nano-range.” It is this music that allows the spider to understand what is happening on its web in minute detail “and that is why the fiber is so pure, both structurally and molecularly,” Vollrath suggests. He pauses.

“We are learning more and more all the time,” he says, with characteristic vigor, about a substance that has developed over many millions of years. In that time, spiders have been confronted with versions of all the structural and molecular issues that trouble the best polymer scientists (and architects and neurobiologists) in the world, he suggests. “And what they have come up with are perfectly evolved solutions.”